1. Field of the Invention
The present invention relates to the field of internal combustion engines and more particularly to that of gas turbine engines as used in aviation, especially on helicopters. It concerns the treatment of the intake air of such engines.
2. Description of the Related Art
A helicopter may be required to maneuver in an environment heavily charged with free particles, for example of sand or dust. When it is close to the ground, during takeoff or landing, it raises and causes to be suspended in the air a large quantity of particles which are ingested by the engines. The engines suffer from impaired performance and are subjected to serious corrosion by the particles passing through them.
In order to restrict this phenomenon, it is known to provide devices, referred to as sand filters, for treating the intake air of the engine, by means of which the particles suspended in the aspirated air are separated therefrom and evacuated.
A known sand filter is of the vortex type. It comprises a parallelepipedic or annular chamber in which are disposed tubular filtering elements crossing from one wall of the chamber to the other, in which filtering elements the air is subjected to a swirling motion. A first, axial, outlet communicates with the inlet channel of the engine and a second, lateral, outlet opens into the interior of the chamber. The interior of this chamber is ventilated to ensure that the air charged with particles is evacuated to the outside.
The ventilation, referred to as secondary, is effected by a device for impelling the air charged with particles, the throughput of which device may amount to as much as 10% of the throughput of the engine.
The known devices include a fan driven by an electric motor, the electrical energy being drawn from the engine itself or from the helicopter. The current supply requires cutoff, control and protection systems. Thus, although this device is very flexible, allowing the power demand to be managed according to the needs and phases of flight, it is relatively heavy and inconvenient to install from the point of view of wiring and electrical control.
Another known solution consists in providing ventilation by means of an ejector using a venturi. The flow required to operate the ejector is drawn from a high-pressure stage of the engine. This system has the advantage of being very reliable and having relatively low weight. However, the take-off from the high-pressure stage is very costly in terms of performance, and reduces the flight envelope of the engine.